Mammalian taste bud structure and function are critically dependent upon proper innervation. The long-term goal of proposed studies is to understand the role that environment has on determining the structure and function of taste buds and nerves following loss of gustatory innervation at adulthood. Neurophysiological, morphological, and behavioral experiments are planned to study the plasticity of the adult gustatory system and processes involved in degeneration and regeneration of taste neurons and associated receptors. An animal model will be exploited in which profound, and specific, functional alterations to sodium salts occur in both regenerating and uncut taste neurons. Neurophysiological taste responses from single chorda tympani nerve fibers will be recorded in control rats and rats fed a Na Cl- deficient diet after unilateral sectioning of the chorda tympani nerve at adulthood. Such recordings will be done in concert with manipulation of voltages across the lingual epithelium. Multifiber recordings of taste responses are also proposed in which the period of dietary restriction will be systematically manipulated post nerve sectioning. Along with these neurophysiological studies, coordinated morphological experiments are planned in which geniculate ganglion cells that innervate single fungiform papilla will be fluorescently labeled before and after nerve sectioning. The proposed studies will provide new information on: 1) the site of response alterations and changes in the density of transducing elements in taste receptor cells as a result of nerve sectioning coupled with dietary sodium restriction, 2) the period during which the adult gustatory system is susceptible to environmental manipulations after unilateral chorda tympani nerve section, and 3) the effects of time, dennervation, and dietary sodium restriction on the stability of gustatory receptive fields. Thus, the findings from these studies will provide new information on the plasticity of peripheral taste responses and the neuroanatomical organization of the peripheral gustatory system. They will also provide important findings for understanding human taste disorders following nerve sectioning.